1. Field of the Invention
The present invention relates to an apparatus and method for radiating laser light to a processing target to process the processing target.
2. Related Background Art
Conventionally, for example, ink has been used to mark the date of manufacture or a serial number on, for example, cans. However, when ink is used, there are problems in that the ink peels off or environmental pollution occurs. As a method of solving the problems, laser marking has drawn attention. The laser marking focuses and radiates laser light to form minute holes in a processing target, such as a can, thereby marking, for example, alphanumeric characters.
As a laser marking method, generally, any of the following methods has been used: a method of using one laser beam to form dots one by one; and a method of arranging an intensity mask with respect to a wide laser beam and collectively performing laser processing. However, in the former case, since the dots are formed one by one, processing takes a long time. In the latter case, since laser light shielded by the intensity mask does not contribute to laser processing, a large amount of light is lost.
As a method for solving the above-mentioned problems, a method using a phase modulation type spatial light modulator (SLM) has been considered. That is, a computer generated hologram (CGH) is presented to the phase modulation type spatial light modulator, and each pixel modulates the phase of laser light input to the spatial light modulator. Then, the phase-modulated laser light is focused on a processing target by an imaging optical system, and the processing target is processed with a processing pattern formed by the focused image. The hologram presented to the spatial light modulator corresponds to the processing pattern of the processing target. In this way, the loss of light is reduced, and it is possible to collectively process multiple points on the processing target.
As shown in the flowchart in FIG. 11, in the laser processing method using the phase modulation type spatial light modulator, first, a desired processing pattern for the processing target is determined, and calculation is performed on the basis of the processing pattern to make a hologram. Then, the hologram is transmitted to a driving unit of the spatial light modulator, and the driving unit presents the hologram to the spatial light modulator. Thereafter, laser light is incident on the spatial light modulator (see JP-A-2006-113185).